Bot flies (Order Diptera, Family Cuterebridae) are large, stout bodied, hairy flies that resemble bumblebees. The botfly egg is deposited by a mosquito or sometimes by another insect. The larva grows in the host's body until it is fairly large. The botfly larva can easily be killed by taking away its air supply -- by putting vaseline or similar on the skin where the lump is, but then you still have to extract the larva. Adult botflies have nonfunctional mouthparts and do not feed. Larvae of this species parasitize wild and domestic rabbits. Females deposit their eggs in or near the entrance of their host's burrow. Bot fly larvae penetrate their host through the skin or natural body openings after hatching. The larvae form a tumor (called a warble) in the subdermal zones of their host and remain at this location until larval development is complete. Larval development varies among species, ranging from 20 to 60 days. Before pupating, the larvae leave the host's skin and drop to the soil.
Generally, the host is not severely damaged by this parasite. The majority of the injury occurs when the larvae exit the host through the warble. Parasitism by the botfly does not affect the edibility of the rabbit (assuming you eat rabbit), generally the area adjacent to the warble is trimmed away, and the rest of the rabbit is suitable to eat.
Is there such a thing as a human bot fly? Yes, we're sorry to say there is. Called the torsalo, Dermatobia hominis, occurs in Mexico and Central America. Fortunately, getting one is an extremely unlikely occurrence for the average visitor.
